This morning, I had another MRI. I am probably one of the few people I know who actually enjoys MRIs; I like the whole futuristic feel, plus the science intrigues me. So, you get to read a bit about it before I get to the main point of this post…

So, MRI, or Magnetic Resonance Imaging, works through the use of a huge magnet. The units of measure for magnets are tesla and gauss; basically, 1 tesla = 10,000 gauss. Well, the earth puts off a magnetic field of 0.5 gauss. The high end MRIs use a 3 Tesla magnet, or 30,000 gauss, so it is pretty powerful. Magnet fields also increase as your near the source (in this case the giant magnet). T3 MRIs will quite easily pull metal objects out of your hand and across a room.

Ok, so the magnet itself is a Superconducting Magnet. It is made up of coils of wire, through which electric current is passed to create the magnetic field. The wire is also kept in liquid helium, which keeps the temperature at about 452 degrees below zero. The whole magnet is kept in a vacuum, which acts as insulation. (The cold temperature increases the efficiency of the machine, because the resistance within the wires drops down to zero).

Well thats all well and good, you go in the middle of a supercold magnet that weighs several thousand pounds, now for the Resonance part of MRI. Ok, well the human body (like anything else…) is made up of billions of atoms, each spinning in every direction. The MRI interacts only with hydrogen atoms, this is because hydrogen has only one proton, and a relatively long magnetic moment, which basically means that it has a strong tendency to line up with the direction of a magnetic field. The MRI’s magnetic field runs lengthwise along the bore ad so when a person is placed in the field, all the hydrogen atoms line up towards the feet and head.

Then, the MRI machine applies a Radio Frequency that only affects the hydrogen atoms. The Radio Frequency is emitted in a pulse directed at the area being examined. This pulse causes the protons in that specific area to spin in a different direction at a specified frequency (this is called the Larmour Frequency). The Radio Frequency is applied through a “coil,” which looks like a mini-MRI that just encloses the target area. There are also three gradient magnets that can be turned on and off very fast in a specific pattern. By doing so, the magnetic field is altered in a very specific area allowing images to be taken like slices of bread, but they are that are only millimeters thick.

So the Radio Frequency gets the hydrogen atoms spinning in a very specific area. Then, the Radio Frequency is turned off, and the hydrogen alines itself with the magnetic field again, releasing all the excess energy. This release of energy is a signal that can be picked up by the coil and sent to the computer system

The computer is able to take this information and convert it into images of the area in question.

Well, all that to say, I had another MRI of my knee today, but the earliest available doctor’s appointment was July 16………. sigh……….

Today, a huge Stratospheric weather balloon did a 13 hour flight for some sort of research. It could be seen across New Mexico and Arizona. It was pretty neat, cause after the sun went down, it was high enough that the sun was still hitting it, so it glowed. Anyway, here is a video of the launch:

So, if you haven’t noticed, sometimes when I post links here, its really just so I can easily find the link again. Like this one: its an inflatable waterproof covering that goes over cases, braces, or incisions so you can still shower or swim or whatever.